1. Field of the Invention
The invention relates to a soft starter device, and in particular to a soft starter device for lamps function according to a similar lumination theory, such as fluorescent lamps, electricity-saving bulbs, mercury-vapor lamps or the like.
2. Description of the Related Art
In a theory of a conventional starting lamp such as fluorescent lamp, an electronic stabilizer is used to start the fluorescent lamp tube with a high voltage and a high current generated due to a high frequency oscillation. At starting, voltage difference between both ends of the fluorescent lamp rapidly increases to a momently high voltage of more than 1,000V, thereby starting the lamp tube. If the filaments of the lamp tube are not preheated, a momently high voltage of over 2,000V is required for starting. As a result, the filaments of the fluorescent lamp must momently withstand a high voltage of more than 1,000V, causing inactive ions created by the preheated filaments to evenly emit to forcedly light up the lamp tube, such that the filaments are speedily oxidized, damaged, aged. Consequently, the life of service of the lamp is reduced. Furthermore, after the fluorescent lamp is discarded, a great amount of mercury filled therein will cause a problem of environment pollution.
To increase the life time of fluorescent lamps used, a conventional method uses a frequency-changing circuit to lower frequency before generating a high voltage, thereby generating a lower voltage instead of the high voltage. At the same time, a lower current flows through filaments for preheating. After a period of time, a high voltage is generated to light up a fluorescent lamp tube. Obviously, a disadvantage of the conventional method is that both the voltage and current are constrained, leading to a poor preheating. On the other hand, since a lamp comprises a plurality of fluorescent lamp tubes of different minimum voltages required for lighting Lil themselves, it is possible that some of the fluorescent lamp tubes will be forcedly lighted up at a lower-voltage condition without being preheated. Since the conventional frequency-changing soft starter device cannot completely stop a voltage input during a filament is preheated, some fluorescent lamp tubes will be lighted up and thus short life time of the tubes cannot be fully prevented.